MTS Server was replaced by Oracle Shared Server beginning with the release of Oracle 9i. The dispatcher for each multi-threaded server registers with all listeners designated by the mts_listener_address init.ora parameters. When a connection request is made, the client interface code randomizes among listeners within the same community.
The listener redirects the client connection request to the least-used dispatcher, which connects the client to a shared server process.
Similarly, the clients that want to connect to a dedicated server randomize their connection requests among the listeners on the same protocol for that server as listed in their tnsnames.ora. The randomly selected listener spawns a server process and hands off the incoming connection to the server.